1. Field of the Invention
The present invention relates, in general, to electronic scales and, more particularly, to an electronic scale having the function of compensating for changes in air pressure so as to precisely measure weights even in an environment in which internal air pressure easily changes as in the case of a glove box.
Further, the present invention relates to an electronic scale having an air pressure change compensation function, which can also be applied to an electronic weighing apparatus equipped with a load sensor having a load cell, as well as to an electronic scale which generates electromagnetic force opposing a load on a plate and detects the load on the plate based on the magnitude of the generated electromagnetic force or the like.
2. Description of the Related Art
Generally, in electronic scales, a measuring plate fits on a load detection unit, and a load acting on the measuring plate is detected by such a load detection unit.
Further, in order to perform averaging and digital filtering, detected data is input moment by moment to a data processing device such as a microcomputer. Such input data is converted into a weight, and this weight is displayed as a measured weight on a display unit.
An example of the above conventional electronic scale includes, for example, the “electronic scale” disclosed in Korean Utility Model Publication No. 20-0419363 (date of registration: Jun. 13, 2006).
That is, the electronic scale of the above Korean Utility Model Publication No. 20-0419363 employs a scheme wherein a reduction in the weight of a material being measured is detected, and is capable of transmitting a signal when a preset value is reached. In detail, when a load is detected by a detection sensor as being equal to or less than a preset load, the electronic scale implements a system for generating a signal, transferring a signal to an Integrated Circuit (IC) unit, calculating the signal at that time using the IC unit, and generating a signal such as a warning lamp or on/off light signal. Therefore, in a facility or the like equipped with a system for periodically replenishing and continuously supplying material such as powder or liquid, there can be provided an electronic scale capable of efficiently performing management and handling related to the operation of the facility in such a way that when the material is continuously consumed and the amount of material decreases gradually, the electronic scale is capable of signaling a worker at the suitable time, that is, before all of the material is exhausted, and the material can be effectively replenished at the proper time.
Further, another example of the above-described conventional electronic scale includes, for example, the “electronic scale and method of controlling the same” disclosed in Korean Patent Laid-open Publication No. 10-2009-0123724 (date of publication: Dec. 2, 2009).
That is, the electronic scale disclosed in Korean Patent Laid-open Publication No. 10-2009-0123724 relates to an electronic scale and method of controlling the electronic scale, in which a weight corresponding to a percentage, weight (%) or a ratio input by a user is displayed. This electronic scale is characterized in that it includes an input unit for inputting ratio information from the user, a measurement unit for measuring the weight of a material, a microprocessor for converting the weight measured by the measurement unit according to the ratio information input to the input unit, and a display unit for displaying the converted weight under the control of the microprocessor.
In detail, the above Korean Patent Laid-open Publication No. 10-2009-0123724 is intended to provide an electronic scale which displays a weight (%) or a percentage that is the relative amount of each of a plurality of materials or displays a weight corresponding to the ratio input by the user, in order to solve the following conventional problem. That is, the problem is that even if, in the case of recipes for cooking, confectioneries, and baking, the amounts of materials are displayed based on the specific number of persons (for example, four persons), the conventional electronic scales merely measure the absolute weight of each material, so that when a user must cook with an amount of material that is larger or smaller than a reference amount, the amounts of all materials must be separately calculated according to the ratio of the materials.
However, the electronic scales disclosed in Korean Utility Model Publication No. 20-0419363 and Korean Patent Laid-open Publication No. 10-2009-0123724 do not describe methods of compensating for errors that may occur for a variety of internal or external reasons.
In this regard, a further example of the conventional technology includes, for example, the “electronic scale capable of compensating for errors attributable to eccentricity and inclination” disclosed in Korean Patent No. 10-0388940 (date of registration: Jun. 12, 2003).
That is, the “electronic scale capable of compensating for errors attributable to eccentricity and inclination” disclosed in the above Korean Patent No. 10-0388940 relates to the electronic scale for, when a plate on which an object to be weighed is placed is inclined, correcting measurement errors attributable to this inclination while compensating for the eccentricity of the object to be weighed, thus enabling a load to be precisely measured.
For this, the above patent No. 10-0388940 discloses an electronic scale characterized in that it includes a base plate, an upper plate, a plurality of vertical component force load cells, a vertical component force bridge circuit, a load output unit, a plurality of horizontal component force load cells, and at least one horizontal component force bridge circuit. The upper plate is arranged on the top of the base plate and allows an object to be weighed to be placed thereon. Each of the vertical component force load cells includes at least one vertical component force sensor which is disposed between the base plate and the upper plate and is subjected in the direction of gravity to the load of the upper plate with the weighing object placed thereon, and which has a resistance that varies with a variation in its external shape caused by the load. The vertical component force bridge circuit is configured to include the individual vertical component force sensors. The load output unit calculates the load of the object to be weighed based on a vertical component force voltage output from a predetermined location in the bridge circuit. Each of the horizontal component force load cells includes at least one horizontal component force sensor which is arranged in the lateral direction of the upper plate and is subjected in the direction of the surface of the upper plate to a horizontal component force by the upper plate inclined with respect to a horizontal direction, and which has a resistance that varies with a variation in its external shape caused by the horizontal component force. The at least one horizontal component force bridge circuit is configured to include at least a part of the horizontal component force sensors. In this case, the load output unit calculates the load of the object to be weighed based on a horizontal component force voltage output from a predetermined location in the horizontal component force bridge circuit and the vertical component force voltage output from the predetermined location in the vertical component force bridge circuit.
However, since the above-described conventional electronic scales calculate the weight from changes in the pressure that an object to be weighed applies to a load detection sensor, changes in surrounding air pressure may influence the weight measured by the electronic scales when there are changes in the surrounding air pressure, but those conventional electronic scales never take such a situation into account.
In this case, in a normal air pressure environment, since a change in air pressure occurring over the short period during which a weight is measured is significantly small, there is no need to especially take such a change into account.
However, for example, in an airtight space having a small volume, such as a glove box, as a worker uses the glove, the internal pressure changes moment by moment.
Therefore, since in such an environment the differences in air pressure change the weight of an object to be weighed, it is impossible to precisely measure the weight when the conventional typical electronic scale is used, thus increasing measurement errors.
That is, in an airtight space such as the glove box, internal air pressure is easily changed, so that such air pressure changes result in immediate measurement errors for the conventional electronic scale.
Therefore, in order to suppress such errors, changes in the air pressure inside the airtight space when the weight is being measured must be minimized, but it is difficult to achieve such minimization in the narrow space in which the glove is mounted.
Furthermore, because the conventional typical electronic scale does not have the function of detecting a change in air pressure and compensating for the weight difference corresponding to the air pressure change, a problem arises in that a large error occurs in the measurement of weights using the electronic scale, for example, in an environment in which internal air pressure changes such as in a glove box.
Furthermore, the conventional electronic scale is also problematic in that when a weight is measured, for example, in an environment in which air pressure changes moment by moment, as described above, the weight displayed on the display unit also changes moment by moment, thus making it very difficult for a user to observe the measured weight with the naked eye.
Therefore, in order to solve the problems occurring in the measurement of weights using the conventional electronic scales, an electronic scale must be provided with the function of sensing a change in an air pressure in an environment in which internal air pressure changes such as in a glove box, and compensating for a weight difference corresponding to the change. Accordingly, it is preferable to provide an electronic scale that enables a weight displayed on the display unit to persist for a predetermined period of time so that the user can easily observe the displayed weight, even if the measured weight changes moment by moment, while always precisely measuring weights even in an environment in which air pressure changes moment by moment. However, such an electronic scale that satisfies all of those requirements has not yet been provided.